In opto-electronic integrated circuits for communication and optical signal processing applications, it is desirable to have beam splitters or directional couplers in semiconductors to combine or split the optical signal. The two common approaches for implementing this are by the use of dual-channel waveguide couplers and by the use of Y-couplers. These techniques, however, usually require 0.5 to 1 cm device lengths which is prohibitively large for opto-electronic integration on a monolithic semiconductor integrated circuit chip.
Recently, P. Buchmann et al, Proc. 3rd European conf., ECIO, 1985, have reported totally reflecting waveguide mirrors in single-mode n/n+GaAs rib waveguides to change the light propagation direction by 90.degree.. They have indicated small size and low insertion loss in these devices.